Radio remote control



March 18, 1941. D. G. c. LUCK 2,235,768

RADIO REMOTE CONTROL Ff G 6 OUTPUT 7 W 15 TB}? I \l fil .k P F'u; 'I'ER I 1 142 'Jnnentor David G. C. Lucli Cittornen 4 Sheets-Sheet 4 D. G. C. LUCK RADIO REMOTE CONTROL Filed Jan. 31, 1939 March 18, 1941.

' 50 which are arranged to prevent currents from the same difference frequency as any other pair.

Patented Mai-.18, 1941 2,235,768

UNITED STATES PATENT-OFFICE RADIO REMOTE CONTROL David G. c. Luck, Oaklyn, N.,J., assignor to Radio Corporation of America, a corporation of Dela- Application January 31, 1939, Serial No. 253,889 13 Claims. (01. 250-2) This invention relates to radio remote control The outputs of the second, fourth, and sixth and more especially to an impulse type of rebufler stages are applied to the first or No. 1 mote control which is not easily deciphered. balanced modulator 21. Th outputs from the Numerous types of remote control by radio first, third, and fifth buffer stages are applied to have been proposed. Controls of this type may the second or No. 2 balanced modulator 29. The be used in directing mobile vehicles such as airbalanced modulators are both connected to a craft. It is important that the control be suitmaster oscillator 3! which supplies currents of able for operating a number of functions, be frequency is which, by way of example, may be fast operating, be operable through interference 30 meg cy les per s cond. The output of No. l and be not easily deciphered. d a r s app d ugh a filter 31% to a 19 It is one of the objects of the invention to No. 1 p fi 3 The output of-the No. 1 amprovide means for remotely controlling by radio. plifier 31 is applied through a filter 4| to an It is another object to provide means for radio n na 45! Th pu of No. 2 modulator 2! remote control in which simultaneous impulses is pplied through a filter 35 to a No. 2 amplifier 1-3 are transmitted on two or more frequencies. 7 39. The output of the No. 2 amplifier 39 is ap- It is another object of the invention to proplied through a filter 43 to the antenna 45. vide means for remotely controlling by several The pe ati n t e tr smit er is as follows: radio impulses of short duration which are in- If k y l i ily closed. the Output fr m terieeked in efi'ect, buffer 1 isimpressed upon modulator No. 2 in 30 A further object is to provide means for re- Which e p s of t e O c llator 2| and the motely controlling by radio a number of funcmaster oscillator M are combined, that is, the tions in any required order, derived current is of side band frequencies, The invention will be described by referring f0+f1) and f0-. 1 Currents 1' f q ency to the accompanying drawings, in which fa-41) Pass thr u h the fil r 35, a e mplified Figure 1 is a schematic diagram of the remote and radiated from the antenna 45. At the same control transmitter, time, currents of frequency is from buffer ii are Figure 2 is a modification of the transmitter, app i d to m dula N i where h y a om Figures 3 and 4 are details of the transmitter, bined with currents of frequency Jo to form our- Figure 5 is a schematic diagram of the receiver rents of freq s f0-ia) and (fe+.fa) This of the invention, current (lo-H s) is passed through the filter 33, 30

Figure 6 is a detail of the receiver, and the amplifier 3i and the network 4!, and is also Figures '7 and 8 are sectional views of the key rad ated by the antenna #5. The networks interlocking means. and t3 keep the impulses of different frequency Referring to Fig, 1, three snap key r snap from combining in the output circuits of the switches I, 3, 5 and connected as follows: The a pl fi s hus n t e y te described. imfirst key I is connected to the first i and sixth pulses of two different frequencies are simulll of six buffer stages. The second key 3 is contaneously radiated by us ng y o sw tc es of nected to the econd l3 a d third [5 buffer the snap contact type to control the transmitter. stages. The third key 5 is connected to the The pu ses are pr a y d of y sh rt 40 fourth H and fifth I 9 buffer stages. Three oscilduration, by way of example, of the order of a 40 lators 2t, 23, 25 are connected as follows: The f w l e n s.

first 2| is betwe n the fir t and s d bufl'er In the event that either of the other keys 3, 5 stages; the second 23 is between the third and are Operated. n r P r f imp l s f a differfourth buifer stages; and the third is between the cut frequency m in ion will be simultanefifth and sixth buifer stages. The oscillators ousiy radiated. Thus, three different combina- 45 supply continuously currents of frequencies fi, tions of pulses operated at different fre is and fa. By way of example, these frequencies re arranged so that they m be adiated in may be 2, 2.01, and 2.02 megacycles per second, distinctive pairs. It is preferable that no pair The buffer stages are preferably thermionic tubes of pulses have the same sum frequency or the oscillators being applied to the modulators 21, 29 By applying this rule for the selection of freduring key-open periods. During key-closed quencies, greater freedom from interference and periods, the oscillator currents are applied to the deciphering is experienced. High amplifier modulators through the buffer stages which are eiliciency may be maintained by transmitting keyed. only one signal at a time through each ampli- 55 fying channel. Using three modulating frequencies h, f: and Is, there are fifteen possible pair combinations, but, of these fifteen, only two groups of three pair are within the rule of the maximum safety from deciphering and at the same time permit the amplifiers to operate most efiiciently. The other nine possible combinations may be used if safety and efficiency are unimportant.

In order that a given combination be made as diificult to decipher as possible, the available safe combinations may be varied by employing one or more keying arrangements, as represented in Fig. 1, or the alternative arrangement shown in Fig. 2. In Fig. 2, the first key I is connected to the second I3 and fifth I9 buffers; the second key 3 is connected to the first 1 and fourth I1 buffers; and the third key is connected to the third I5 and sixth II buffers. of the circuit corresponds to the circuit of Fig. 1. If different combinations are used at the transmitter, it should be understood that a corresponding change is required at the receiver in order that the same keys control the same functions.

The detailed connections for each oscillator and its connected buffers are shown in Fig. 3. The triode portions of a pair of thermionic tubes 5!, 53 are connected, in parallel, to a piezoelectric crystal 55 and maintain it in continuous oscillation. Grid electrodes, regulating the electronic coupling from the triode sections, are keyed by the switches I, 5 which correspond to the keys previously described. Connections are also made to the other oscillator buffers, as are indicated by the leads 51, 59. The output connections preferably include resonant circuits 6|, 63 which are coupled, respectively, to modulators No. 1 and No. 2, as shown in Fig. 1. A recycle switch 64 is connected in the C battery lead to permit the switching devices to be reset if the. devices become misarranged by the omission of a cycle, or the like.

The master oscillator and modulator circuit connections are shown in Fig. 4. The master oscillator is preferably controlled by a crystal 65, which may bearranged to oscillate at its third harmonic, 15 megacycles per second, near which frequency the network 61 is resonant, and the harmonic frequency may be doubled in the output circuit of thermionic tube 69. The output currents are applied in push-pull to the grids of the balanced modulators 1|, 13. The input from the buffer stages of one set of modulating oscillators is applied through a mutual coupling 15 to the resonant circuit 11, which is connected to control grids in thermionic tubes H, 13 in push-pull. The parallel-connected anode circuits of these tubes include a resonant circuit 19 which is suitably coupled through the filter 35 to the second amplifier 39, as shown in Fig. l. A second balanced modulator including thermionic tubes BI, 83 is connected in parallel to the first balanced modulator H, 13. The input from the oscillator buffers is applied to a resonant circuit 85 which is connected to control grids in the thermionic tubes 8|, 83. The anode or output circuit of the thermionic tubes includes a resonant circuit 81 which is coupled through the filter 33 to the first amplifier 31, as shown in Fig. 1.

The radio receiving device is schematically illustrated in Fig. 5. An antenna IN is connected to a first radio frequency amplifier I03. The first amplifier is responsive to a range of frequencies corresponding to the frequencies of The remainder one group of transmitted impulses fo+fi. fo-Hz, and corresponding, by way of example, to 32.00, 32.01 and 32.02 megacycles per second. The output from the radio frequency amplifier I03 is impressed upon a modulator I which is connected to a local oscillator I01. This local oscillator is preferably operated at the same frequency as th master oscillator in the transmitter. The local oscillator may be operated at any suitable frequency provided it is constant with respect to the transmitter and the balance of the equipment is designed to accept or reject, respectively, currents of the desired or undesired frequencies. The output from the modulator I05 is connected to an intermediate frequency amplifier I09 which is responsive to a range of frequencies extending from ii to fa. The output from the intermediate frequency amplifier is applied to three filters III, H3, II5. These filters are respectively responsive to the frequenciesfi, f2, fa. The outputs of the three filters are applied to one of the input circuits of rectifier and locking devices H1, H9 and III, which will be hereinafter described.

The antenna is also connected to a second radio frequency amplifier I23, which is responsive to the lower of the transmitted frequency groups, for example, 27.98 to 28.00 megacycles per second. The output of the second radio frequency amplifier is connected to a modulator I25 which is connected to the local oscillator I61. The modulator output is applied to a second intermediate frequency amplifier I21 which is responsive throughout the frequency range If to is. The second intermediate frequency amplifier is connected to filters I29, I3I', I33, which respectively pass currents of the frequencies f1, f2 and is. The outputs of the last-mentioned three filters are applied respectively to the input of the rectifier and lock devices H1, H9 and I2I. The outputs of the rectifier and lock devices are applied to toggle circuits I35, I31 and I39, which will be hereinafter described. The output from the toggles may be applied to relays or other devices whose function is to be controlled by the "transmitted pairs of impulses. Connections of the pairs of filters of the two channel groups to the function controlling devices I35, I31, I33 must correspond to those from the function-selecting switches I, 3, 5 to the buffers of the two channel groups at the transmitter.

The rectifier, lock and toggle devices are represented by the schematic circuit diagram of Fig. 6. The filter inputs are applied through capacitors I36, I38 to a pair of control electrodes I40, I42 of a thermionic tube MI. The control electrodes are connected respectively to a C battery through resistors I44, I46. The values of resistance and capacitance are preferably so chosen that their respective time constants will be of the order of the impulse duration, and so that impulses of less than half normal duration will not cause operation of the rectifier and lock. The rectifier and lock tube is so biased that it requires the simultaneous application of the two transmitted impulses to permit rectification within the tube. The rectified signals are derived in the output circuit and are applied .to the input circuits of a pair of tubes I43, I45. These tubes are so connected that a steady current flows only in the output circuit of one of these tubes at a time, depending upon the application of potentials to their input circuits. In effect, the tubes I43, I45 operate as a toggle. The theory of their operation is substantially that of the multivibrator except that they are not self-oscillatory but aperiodic and operate onlyupon the application of triggering impulses. The toggle device s described in U. 8. Patent No. issuedtoW.R.K ochonAusust assigned to the same application.

The theory of operation of the receiving system is as follows: The simultaneously transmitted pairs of impulses are received and amplified, respectively, in the first or second radio frequency amplifie depending upon the frequency of the received impulses. The amplified currents are converted from currents corresponding to upper and lower side band frequencies into currents of intermediate frequency which correspond to the transmitter oscillator frequencies I1, I: or Is. The intermediate frequency currents will be passed by the filter corresponding to their original frequency and rejected by the other filters. Thus, there will appear in the output of the filters currents of two frequencies corresponding to h, f: or is. Depending upon their frequency. these currents will be simultaneously applied to one of the rectifier and lock devices. The rectifier and lock device which is operated by any particular pair of impulses will correspond to one of the snap keys I, 3 or 5. The output currents may be used to actuate a relay in either the operative or inoperative position oiin either of two operative positions. It should also be understood that the derived currents may be used to actuate a step-by-step relay in place of the electronic toggle, if sequential rather than alternate on and ofi control of any function be desired, or any suitable instrument for controlling the several functions.

Thus, the invention has been described as a remote radio control in which a pair of impulses of different frequency are simultaneously transmitted. The received pulses depending upon their respective frequencies are used to selectively control a locking device which is only responsive to the two particular frequencies when they are simultaneously applied. The locking device in turn controls a relay which governs the function to be remotely controlled. It should be understood that the invention is not limited to the control of three functions as the same system may be expanded to include a larger number of operations; in fact, one oi the practical advantages of the invention, economy of apparatus, is only fully realized when a considerable number of functions are controlled. It should also be understood that while two simultaneously transmitted pulses of unrelated frequencies are used to provide safety from deciphering, the system may be made even more safe by using three or more simultaneous pulses of unrelated frequencies. It is apparent that it will be difiicult to decipher the operation of the device because the controlling radio waves are of many different frequencies and each is only radiated for a very brief interval which makes analysis most difficult. Furthermore, the frequency of the controlling pulses is continuously 2,050,059 which 4, 1936, and is assignee as the instant changing in what may be a very large number of different combinations. It is desirable to use interlocked switches or keys at the transmitter to prevent simultaneous transmission of undesired combinations of impulses. The interlocking may be accomplished by mechanical or electrical means.

One form of mechanical interlock for the keys I, 3, i is shown in Figs. 7 and 8. The key knobs plate are ofi'set so Iii, I, I5! are provided with shafts I51, I59, IBI which include bulging portions I83, I65, I61. These portions pass freely through aligned apertures in fixed plates I89, Ill. A slidable plate with separable sections I13 is arranged within the fixed plates. The apertures in the slidable that only one aperture in the slidable plate will be aligned with a pair of aligned apertures in the fixed plates by the movement of the bulged portion (for example, portion I65) of any one shaft. The misalignment of the remaining apertures in the slidable plate prevent the operation of the remaining keys until the operated key (for example, key I53) has been released.

I claim: v

1. In a control system means for transmitting a pair of impulses of different frequencies, means for receiving said impulses, rectifying means re sponsive only upon the simultaneous application of said pair of impulses for deriving from said pair a single impulse, and means responsive to said single impulse.

2. In a radio remote control system means for radiating a pair of impulses of different frequencies, means for receiving said impulses, means solely responsive to the simultaneous application of said pair of impulses for separating said impulses, means for rectifying said separated impulses to derive therefrom a single rectified impulse, and means responsive to said single impulse to effect said control.

3. In a radio remote control system means for radiating simultaneously a pair of radio impulses of different frequencies, means for separately receiving said impulses, a rectifier and lock device, means for simultaneously applying said received pair of impulses to said rectifier and lock device to derive therefrom a single controlling impulse, and means for applying said single impulse to a device to be controlled.

4. In a remote control system a transmitter, means for deriving from said transmitter impulses of short duration and different frequency, means for transmitting said impulses, means for receiving and separating said impulses, a rectifier including locking means, said locking means being so constructed and arranged that said rectifier responds only upon the simultaneous application of said impulses of difierent frequency, means for applying said separated impulses to said rectifier and locking means and deriving therefrom single controlling impulses, a toggle device for alternately starting and stopping current fiow in accordance with the application of successive ones of said controlling impulses, and means for utilizing said currents.

5. In a remot control transmitter means for generating impulses of a plurality of different frequencies, a pair of balanced modulators, a master oscillator connected to said modulators,

means for applying simultaneously two of said said modulators respectively to therein modulate said local oscillations. means for deriving from said modulators two impulse currents of diflerent frequencies, a rectifier and locking device, means for applying said last-mentioned currents to said rectifier and lock to derive from two simultaneously applied pulses asingle recti fled pulse, and means responsive to said single imp-alsefor controlling a selected function.

from said balanced modulators respectively im-' pulse currents corresponding to upper and lower side band frequencies, means for transmittingsaid last-mentioned impulse currents and a receiver including means for receiving separately imp es of different frequencies, a local generator f oscillations, a pair of modulators connect to said oscillator, means for applying two of d separated impulses to said modulators respectively to therein modulate said local oscillations, means for deriving from said modulators two impulse currents of difl'erent frequencies, a rectifier and locking device, means for applying said last-mentioned currents to said rectifier and lock to derive from two simultaneously applied pulses a single rectified pulse, and means responsive to said single impulse for controlling a selected function.

8. The method of remote control which includes transmitting impulses of difierent frequencies, receiving said transmitted impulses,

simultaneously rectifying said impulses to derive a single controlling impulse, limiting the rectification to the simultaneous application of said impulses, and applying said controlling impulse to operate a selected function.

9. The method or transmitting remote control impulses which includes generating a pair of impulses of different frequencies, modulating simultaneously said impulses with a current of another frequencyto obtain impulse currents of and applying said single impulse current to control a function.

11. The method of remote control by impulses which includes generating a pair of impulses of diiferent frequencies. modulating said impulses .with a current of another frequency to obtain impulse currents of the modulation frequencies. deriving from said currents of modulation frequencies impulses of frequencies corresponding to an upper and a lower side band frequency, and transmitting said last-mentioned impulses, separately receiving said impulses of upper and lower side band frequency, generating local oscillations, modulating said local oscillations by said received impulses, deriving from said modulations separate impulse currents of two differentfrequencies, simultaneously rectifying said currents to obtain a single impulse current, and applying said single impulse current to control a function.

12. In a system of the character of claim 1, means for interlocking said transmitter to prevent transmission of other than the desired impulses.

13. In the method described by claim 8, the additional step of preventing transmission of other than the desired impulses.

DAVID G. C. LUCK. 

